You'll find a number of us are running a dual-boot configuration, and thus yes have been able to make clear comparisons on identical hardware. Personally went from Vista 32-it to Win7 64-bit, so performance comparisons are even more extreme.
In a nutshell, Win7 utterly blows Vista away in terms of performance and stability. Home networking greatly simplified, additions to taskbar make life much easier. Even moving to x64, driver support a huge step-up from when Vista was first rolled out. Collaboration btwn CPU and GPU (vid-card processor) first-of-its-kind - thus nVidia recently hailing Win7 as the "next gaming platform".
Now don't misread me... am not some fanboy claiming the "perfect OS". Not really sure that will ever exist. But, it is worth the move IMHO.
Words to the wise:
If you can make the move to x64 Win7, do so.
A clean install is always better than an "upgrade" install - and if moving from x86 (32-bit) to x64, you don't get the "upgrade" option anyhow.
Round up your core drivers BEFORE you install a new OS.
Don't trust an OEM to provide the latest/best drivers... do the legwork yourself.
If you can afford to go Pro builds, do so... will give you MUCH greater tweakability